Download Homeostasis - INAYA Medical College

Physiology
232 BMS
Dr/Nahla Yacout
2015/2016
 What is physiology?
 Why is the study of human physiology so important?
 What is homeostasis?
 Regulation of body functions
Chemical
(Hormonal)
Nervous
Autoregulation
Definition
Definition
Definition
Characteristics
Characteristics
Characteristics
Example
Example
Example
 Feed back control system (Negative – Positive)
 Is the scientific study of normal body function
(How cells, tissues, organs & body systems work when
they are in a healthy state, EX: How is the heart beat
produced, How is the heart rate regulated & how the
organism as a whole accomplishes particular tasks
essential to life)
 The physiological mechanisms that we study are not
unique to humans & may not be unique to mammals in
general, but they were discovered firstly in non-humans
(As:mice).
Why is the study of human
physiology so important?
 Because it is the major scientific foundation of medicine
& other health applications
 We must understand how a cell, tissue, organ or system
normally functions before we can understand how the
physiological processes become altered in a disease or
injury
Pathophysiology
 It is the basis for immunology, pharmacology,
Biochemistry, Microbiology
Physiology
Dealing with the normal
life phenomenon exhibited
by all living organisms
Human physiology
Dealing with the normal
life phenomenon of the
human body
Homeostasis
o Maintainance of relatively constant body’s internal
environment although there are changes in the external
environment
o The physiological processes & regulatory mechanisms
that we study in physiology occur only for
Maintaining Homeostasis
Successful compensation
Homeostasis re-established
Failure to compensate
Pathophysiology, Illness,
Death
Clinical applications
 When we go to a physician for a physical exam, the
nurse or physician will sample our internal environment
to see if we are maintaining homeostasis.
 They usually measure our internal body temperature, our
blood pressure & they may order various blood tests.
 If one or more of these measurements is outside the
normal range, it indicates that homeostasis is not being
maintained.
Regulation of the body functions
In order to reach to homeostasis
Chemical
(Hormonal)
Nervous
Autoregulation
Feed back control system
Chemical (Hormonal) regulation
A regulatory process performed by hormone or active
chemical substance in blood or tissue
Characteristics:
 Responds slowly
 Acts extensively
 Lasts for a long time
A process in which body functions are
controlled by nervous system
Characteristics:
 Responds fast
 Acts exactly or locally
 Lasts for a short time
A process occuring when some mechanism within a
biological system detects & adjusts for changes within
the system
Example:
If blood flow to an organ is decreased, it will return to
it’s normal level within the next few minutes because of
vasodilatation
This autoregulatory mechanism occurs in the absence of
neural & hormonal influences
Feed back control system
Negative feed back control
Positive feed back control
Negative feed back loop
Sensor
Sensor
Effector
Integrating center
Effector
Suppose that you have a room thermostat set at 70 F
(Set point) ---- The room gets cooler ---- A sensor will
detect this ---- Activates a heater (Effector) that will
correspond this deviation or sends the information to an
integrating center which controls the effector
In response to a fall in body temperature ---- temperature sensors
(Found in skin) activate the integrating center (Present in
hypothalamus) ---- the integrating center will activate the effectors
(Shivering skeletal muscles)
In response to rise in body temperature ---- sweat glands
(effectors) are activated
How blood pressure is
maintained within normal range?
Fall in blood pressure (Stimulus) ---- Activates the
sensors (Blood pressure receptors – Baroreceptors)
---- Stimulate sensory neurons that convey the
information to integrating center in the brain
(Medulla oblongata) ---- stimulates motor neurons to
increase the heart rate ---- causes rise in blood
pressure
A person eats a candy bar ---- Blood glucose (sugar)
concentration will raise (Stimulus) ---- Islets of
langerhans in the pancreas (Cells sensitive to the
blood glucose level) (Sensor) will be activated ---Will secrete insulin ---- Insulin stimulates certain
tissues (Adipose tissue, Skeletal muscles, liver) to
take glucose out of the blood ---- & so blood glucose
concentration will decrease
Positive feed back loop
 It operates to amplify changes
 In response to a small change in a particular direction, a
positive feedback loop will cause the change to become
greater & greater
Example:
During birth, Oxytocin causes the uterine muscles to
contract ---- These signals are detected by the
hypothalamus which signals to the anterior pituitary
gland to secrete more oxytocin, leading to more
contractions
Summary

Homeostasis: Is the maintainance of relatively
constant body’s internal environment although there are
changes in the external environment
 Regulation of body functions
Chemical
Nervous
Autoregulation
performed by hormone or body functions are
active chemical
controlled by nervous
substance
system
some mechanism within
a biological system
detects & adjusts for
changes within the
system
Responds slowly
Acts extensively
Lasts for a long time
Responds fast
Acts exactly or locally
Lasts for a short time
Without involvement of
nervous system or
hormone
Example: Blood glucose
Example: Blood pressure Example: Blood flow to
an organ
 Feed back control system
Negative
Positive
Ex: Oxytocin hormone